Decorative laminate surface coverings can be formed into sheets or individual tiles. Typically, in the manufacture of a resilient floor covering, a wear layer is combined with a substrate and resin to form the resilient sheet or tile. The substrate usually comprises a felted or matted fibrous sheet of overlapping, intertwined filaments or fibers. A substantially uniform layer of a liquid or semi-liquid resinous composition containing a synthetic polymeric material, usually an ungelled polyvinyl chloride plastisol and a blowing or foaming agent is typically applied to the substrate. The liquid or semi-liquid plastisol vinyl resin composition is subsequently firmed or gelled at an elevated temperature. This gelled plastisol may be printed with a decorative pattern or design having a blowing or foaming inhibitor for chemically embossing the substrate.
Decorative laminate surface coverings are often designed to have textured surfaces patterned to duplicate a look of actual wood, tile, brick, stone, and other such products. Typically, the texture is either mechanically embossed by pressing a pattern into the surface covering or chemically embossed by using foam retarding agents to restrict expansion of a foamable layer in specific regions of the design. Although these methods provide attractive decorative surface coverings, they are limited in their capability to replicate the appearance of the actual product.
There continues to be a demand by consumers for surface coverings that have a “more realistic” appearance to the natural product. U.S. Pat. No. 5,961,903 describes one method of manufacturing an embossed resinous foam product which is both chemically and mechanically embossed, and includes forming a foamable, resinous composition which contains a blowing agent. An ink composition having a blow modifying agent/retarder is printed onto the foamable, resinous composition. A wear layer is applied and the wear layer/foamable composition is heated to expand the foam and cure the wear layer. Areas of the foam printed with the printing ink composition are restricted from expanding resulting in a chemically embossed product. The chemically embossed structure is cooled to ambient temperature before any further handling. Thereafter, the chemically embossed product is reheated and a texture is mechanically embossed, using an overall textured embossing roll, into the hot wear layer overlying the non-restricted/up foam regions by pressure while it is relatively soft, plastic, and moldable. After the foam is mechanically embossed and has cooled to ambient temperature, a wear layer is coated and cured onto the chemically and mechanically embossed foam.
An alternative method for making a chemically and mechanically embossed surface covering (Armstrong U.S. Ser. No. 09/770,582 incorporated in by reference), includes coating a backing layer with a foamable layer, and adding a print layer to it. The print layer forms a design and a portion of the design is formed with a retarder composition. A thermoplastic wear layer is applied onto the print layer and cured by heat at a temperature sufficiently high enough to expand the foamable layer. The areas of the design layer where the retarder composition is applied are also chemically embossed during such curing. In a continuous process and without cooling to ambient conditions, the temperature of the cured thermoplastic wear layer is adjusted by heating, and the wear layer is then mechanically embossed to have a surface texture in the wear layer overlying the unrestricted/up areas. Optionally, a top coat can be applied to the wear layer before curing and expanding the foam, and the top coat can be mechanically embossed.
Despite existing methods of making chemically and mechanically embossed surface coverings, there is a need for a surface covering having a chemically embossed foam layer and a selectively textured top coat wear layer for simulating a natural product.